Recherche avancée

Sur d’autres sites (8909)

• How can I apply zoom in/out filter on specific frame in video using ffmpeg ?

  4 novembre 2019, par Axita Kathiriya

  I want to apply zoom filter on specific frame on video using ffmpeg.

  for example, I want to make a slideshow of 5 images and each image will take 4-5 seconds for slide. I want zoom in/out effect on each image. So, i want to apply this effect at that time when particular image stay for 4-5 seconds. Please see this video link. I want same result like this using ffmpeg : https://youtu.be/nNTiyRDhlRY please refer first two slides of this link.

• ffmpeg : How does one designate what parts of an overlay video stream let the underlay video stream show through ?

  21 février 2023, par Walt Howard

  Stream 0 is a rotating planet created using povray. (https://www.povray.org/)

  


  Stream 1 is just a static jpeg of stars.

  


  I'm using overlay like this :

  


  nice ffmpeg -i protoplanet.mp4 -i stars.jpg \
         -filter_complex "[0:v]scale=1024:768[scaled];[1:v][scaled]overlay=0:0" \
         -movflags faststart -pix_fmt yuv420p -r 10 planet.mp4


  


  I had it working when I used the output from povray directly. I didn't have to know why that worked, because it just did. However, after adding some post processing to the planet video, the entire video has no alpha channel (educated guess) so the background stream (Stream 1) cannot show through.

  


  The post processing I did was this (which works great) : https://www.reddit.com/r/ffmpeg/comments/im2mkp/creating_a_retro_glow_effect_with_ffmpeg/

  


  But that made the video unable to have an overlay background possibly due to it destroying the alpha channel and turning many of the blacks to dark grey.

  


  I can merge the pure POVRAY output and the background and then add the glow effect, but it adds the effect to the background stars and captions also which ruins the effect to some degree. I want to glo-ify the planet first, then stick it on a pure starfield background.

  


  In thinking this over I may have to recreate the alpha channel after adding the glow effect, using a nearest match to black and dark grey to alpha.

  


  Hmmm. It might be a codec issue as I didn't specify any -c:v in any of my commands....

  


• Imagemagick transitions between multiple images — need idea

  5 juillet 2015, par user3650185

  I am using Fred’s Imagemagick scripts, particularly, fxtransitions to create a transition effect between two images. I am creating jpeg image frames. Later, I will use ffmpeg to turn them into video. It is my third day with Imagemagick and currently I can successfully apply the transition effect between two images with the following script. However, I also need to meet two following criteria :

  $result = shell_exec("bash /cygdrive/path/to/fxtransitions -e  explode -f 50 -d 1 -p 1 -r first.jpg second.jpg output.jpg"); 
  
  echo $result;

  1. Each image must stay for some 9 seconds without distortion and then quickly transforms into the next image.

  2. Currently, Fred’s script allows two image inputs. Is it possible to use more than two images within the script ? How can I loop through multiple images with php ?